Question

Complete the reaction-

A.
B.
C.
D.

Answer 1

Here, $2 -$ethynylcyclohexan$- 1 -$one is reacted with borane, trihydrofuran, and hydrogen peroxide, there is a formation of one product. And that will react with sodium hydroxide and iodine under heat and there will be the final product. The $B{H_3}$reagent is used for hydroboration reaction of alkynes and alkenes. During this reaction, first there is a formation of enol.

Complete answer:
$2 -$Oxo cyclohexane$- 1 -$carboxylic acid is not formed by this reaction. Hence, option (A) is incorrect.
There will not be a formation of $2 -$Acetylcyclohexan$- 1 -$one. Hence, option (B) is correct.
Here, $2 -$ethynylcyclohexan$- 1 -$one is reacted with borane in the presence of trihydrofuran, (THF) and hydrogen peroxide and there is a formation of unstable enol form. The borane is mainly used for the hydroboration of alkynes. Thus, by hydroboration of alkynes, there is a formation of a product called enol which is highly unstable. Therefore, it will react with sodium hydroxide and in the presence of heat, there is a formation of $2 -$($2 -$oxocyclohexyl) acetaldehyde. Let’s see the reaction,

Hence, option (C) is correct.
There will not be a formation of cyclohexanone as the final product. Hence, the option (D) is incorrect.

Hence, option (C) is correct.

Note:
By the hydroboration of alkynes there is a formation of product called enol and this process is known as tautomerization. And this enol is converted into keto form which is more stable aldehyde. The enol is otherwise called, half alcohol. And the constitutional isomer is aldehyde. This type of reaction is called keto – enol tautomerism.